The electrical systems of today's vehicle's are becoming increasingly complex as engineers replace various passive subsystems with so-called active or "smart" subsystems featuring their own logic and control functions. Such smart subsystems may control, for example, the vehicle's antilock brakes and automatic transmission, as well as a variety of subsystems which may be generally referred to as "body circuits." As a result, the electrical system of the typical vehicle includes increasing numbers of discrete, though highly-interconnected, electrical components and logic devices, with a correlative increase in the difficulty with which faults or failures in any one or more of those components and/or logic devices may be successfully and readily diagnosed.
For example, rather than having a simple wiring harness comprising a bundle of dedicated wires through which individualized control signals for each component might be sent from a central processor or Electronic Control Module ("ECM"), the logic of many components is now further responsive to a variety of analog and/or digital signals correlatively generated by any number of other counterpart components within the system. With this high degree of component interaction, the identify of the malfunctioning component becomes much less apparent, and "troubleshooting" a vehicle having a faulty electrical system becomes an increasingly difficult and time-consuming task. And, troubleshooting of these electrical systems is further complicated upon experiencing a short otherwise preventing the powering-up of all or part of the system.
Moreover, the electrical interaction of the various components and devices comprising the vehicle's electrical system is directly affected, not only by the vehicle make and model, but by the particular manner in which that very vehicle is outfitted. This in turn produces variation in the nominal characteristics of the vehicle's electrical system, even when the system is known to be operating in accordance with specifications. Such "normal" variation in the system's characteristics makes the diagnosis of later-occurring faults much more problematic.
Finally, known apparatus and methods for diagnosing faults in vehicle electrical systems also have difficulty addressing the somewhat related problem of intermittent electrical system malfunction due, for example, to the presence of marginal components therein, either as of the time of vehicle manufacture or later, upon deterioration or aging of those components. Add to this the desire to reduce customer inconvenience and warranty expense through preventive maintenance, likewise requiring, for example, identification of such marginal components for replacement or service when the customer brings the vehicle in for regularly-scheduled maintenance.
What is needed, then, is an apparatus and method for diagnosing faults within a vehicle's electrical system which overcomes the aforesaid problems encountered by the prior art.